RFR: 7903542: jextract sample compilation scripts can avoid specifying standard include directory in Mac OS

[Athijegannathan Sundararajan]

jextract infers standard include directory automatically.

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Commit messages:
 - 7903542: jextract sample compilation scripts can avoid specifying standard include directory in Mac OS

Changes: https://git.openjdk.org/jextract/pull/127/files
 Webrev: https://webrevs.openjdk.org/?repo=jextract&pr=127&range=00
  Issue: https://bugs.openjdk.org/browse/CODETOOLS-7903542
  Stats: 31 lines in 29 files changed: 0 ins; 31 del; 0 mod
  Patch: https://git.openjdk.org/jextract/pull/127.diff
  Fetch: git fetch https://git.openjdk.org/jextract.git pull/127/head:pull/127

PR: https://git.openjdk.org/jextract/pull/127